Method, device and system for sending a reset message sequence number during switching

ABSTRACT

A method of sending reset message sequence number is provided. During a connected state handoff of an access terminal (AT) between a source access network (AN) and a target AN, the source AN sends a reset message sequence number of the AT to the target AN. The source AN adds the reset message sequence number of the AT to the message sent to the target AN. Thereby, the problem in the existing systems that, the source AN cannot send the reset message sequence number of the AT to the target AN, and thus the target AN cannot perform a reset process on the AT when the AT is switched from the source AN to the target AN is thus solved. An access network (AN) and a communication system are also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Patent ApplicationNo. PCT/CN2007/003040, filed Oct. 25, 2007, which claims priority toChinese Patent Application No. 200610161003.9, filed Dec. 1, 2006, bothof which are hereby incorporated by reference in their entirety.

FIELD OF THE INVENTION

The present invention relates to the communication field, and moreparticularly, to a method, device, and system for sending a resetmessage sequence number.

BACKGROUND

In a code division multiple access high rate packet data (CDMA HRPD)system, signals are transmitted by using a signaling link protocol(SLP), and information interaction between an access network (AN) and anaccess terminal (AT) is realized by sending SLP message packets betweenthe AN and the AT. Each SLP packet has a corresponding sequence number.The sequence number beginning from 0 is used for determining whether theSLP packet is a retransmitted message. When a reset process of SLP needsto be performed for the AT, the reset process of the SLP is accomplishedby sending a Reset message and a ResetAck message between the AN and theAT. The Reset message and the ResetAck message also have thecorresponding message sequence numbers, and the message sequence numbersof the Reset message and the ResetAck message in the same flow areidentical.

As shown in FIG. 1, the main flow of the reset process of SLP is givenbelow.

In Step 100, an AN initializes the local sequence number of the SLPpacket for the AT (including sending message sequence number andreceiving message sequence number).

In Step 101, the AN sends a Reset message to the AT.

In Step 102, the AT receives the Reset message, and then verifies themessage sequence number of the Reset message.

In Step 103, when determining that the Reset message is valid, the ATfeeds back a ResetAck message to the AN.

On the other hand, when determining that the Reset message is invalid,the AT discards the Reset message.

In Step 104, the AT initializes the local sequence number of the SLPpacket.

In Step 105, the AN receives the ResetAck message, and verifies themessage sequence number of the ResetAck message. For example, if themessage sequence number of the ResetAck message is identical to themessage sequence number of the Reset message delivered by the AN, theResetAck message is considered to be valid.

In the above method, the valid check on the Reset message is performedby verifying the message sequence number of the Reset message, and theverification method is described below. Given that the sequence numberoccupies S bits, if the sequence number is N, [N+1, N+2^(S−1)−1] isconsidered to be greater than N, and [N−2S−1, N−1] is smaller than N.When the AT receives the Reset message, if the message sequence numbercarried in the Reset message is greater than the message sequence numberof the Reset message previously received by the AT, the Reset message isconsidered valid; otherwise, the message is considered invalid.

In the conventional CDMA HRPD system, the AT verifies the validation ofthe Reset message according to the message sequence number of the Resetmessage. Thereby, during a connected state handoff between the ANs,since the source AN cannot transmit the message sequence number of theReset message to the target AN, the target AN cannot perform a resetprocess on the AT. Therefore, the sequence number of the SLP packetsubsequently sent between the AT and the target AN is determined to beinvalid, thus causing packet loss.

For example, if the Reset message sequence number of the AT on thesource AN is 2 and the Reset message sequence number on the AT is also2, after the AT is switched from the source AN to the target AN, sincethe target AN fails to receive the Reset message sequence number of theAT, the Reset message sequence number of the AT on the target AN is 1.When the target AN performs a reset process on the AT, the Reset messagesequence number “1” is sent to the AT, and AT determines that “1” issmaller than the local Reset message sequence number “2,” so that areset process will not be performed, that is, the local SLP datastructure and the corresponding buffer will not be cleared and thesequence number of the local SLP packet will not return to zero. Afterthe source AN sends the Reset message sequence number “1,” the local SLPdata structure and the corresponding buffer of the AT and the sequencenumber of the SLP packet are initialized, so that the AT relevantinformation at two sides are inconsistent. When the target AN sends theSLP packet to the AT, since the sequence number of the SLP packet issmaller than the sequence number of the local SLP packet of the AT, theAT determines that the SLP packet subsequently sent by the target AN isinvalid and then discards the SLP packet, thus causing SLP packet loss.Such a packet loss will trigger failures to receive calls from other ATsor to use subscribed application services, thereby causinginconveniences to subscribers.

SUMMARY

The present invention provides a method of sending Reset messagesequence number, a communication device, and a communication system.

The present invention provides a method of sending reset messagesequence number, which includes the following step.

During a connected state handoff of an access terminal (AT) between asource access network (AN) and a target AN, the source AN sends a resetmessage sequence number of the AT to the target AN.

The present invention provides a communication device, which includesthe following units.

A unit is adapted to confirm a connected state handoff of an accessterminal (AT) to a target access network (AN).

A unit is adapted to send a reset message sequence number of the AT tothe target AN during the connected state handoff of the AT.

The present invention provides a communication system, which includes aplurality of access networks (ANs).

The AT is adapted to establish a connection with a corresponding AN, soas to accomplish data communication.

The plurality of ANs is adapted to enable the AT to access the network.When a connection state of the AT is switched between a source AN and atarget AN, the source AN sends the reset message sequence number of theAT to the target AN, and the target AN performs a reset process on theAT according to the message sequence number.

The present invention has the following advantages.

In the present invention, a reset message sequence number of an AT isadded into a message sent by the source AN to the target AN, thereby,during a switch of the AT from the source AN to the target AN, the resetmessage sequence number corresponding to the AT in the target AN can beupdated in real time, so as to ensure the normal data communicationafter the AT is switched to the target AN, avoid signaling link protocol(LSP) data packet loss during the communication, thus ensuring theservice quality of the AN.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart of the reset process of SLP;

FIG. 2A is a systematic structural view of a communication system,according to an embodiment of the present invention;

FIG. 2B is a functional structural view of a source AN, according to anembodiment in the present invention; and

FIG. 3 is a flow chart of a connected state handoff of an AT between asource AN and a target AN, according to an embodiment in the presentinvention.

DETAILED DESCRIPTION

In an embodiment, during a connected state handoff of an access terminal(AT) between a source access network (AN) and a target AN, the source ANtransmits a Reset message sequence number to the target AN, and thetarget AN performs a reset process for the AT according to the Resetmessage sequence number.

The source AN may transfer the Reset message sequence number to thetarget AN in many different ways. For example, when sending anA16-session Transfer Request Message to the target AN, the source ANadds the Reset message sequence number of the AT into the A16-sessionTransfer Request message. Or, when sending an A16-session TransferComplete Message to the target AN, the source AN adds the Reset messagesequence number of the AT into the A16-session Transfer CompleteMessage. Certainly, a new message may also be used to transmit the Resetmessage sequence number of the AT.

The A16-session Transfer Request Message or the A16-session TransferComplete Message may carry the Reset message sequence number during thetransmission in many different ways. For example, a session stateinformation (SSI) is added into an Information Element of the message tocarry the Reset message sequence number of the AT. Or, a new InformationElement is added into the A16-session Transfer Request Message or theA16-session Transfer Complete Message to carry the Reset messagesequence number of the AT.

Hereinafter the way of using the A16-session Transfer Request Messageand the A16-session Transfer Complete Message to transmit the Resetmessage sequence number is illustrated as an example with reference tothe accompanied drawings.

As shown in FIG. 2A, in this embodiment, the communication systemincludes an access terminal 20 (AT), a source access network 21 (AN1),and a target access network 22 (AN2). The AT 20 is adapted to establisha connection with the corresponding AN, so as to accomplish datacommunication. The source AN 21 is adapted to send the Reset messagesequence number of the AT 20 to the target AN 22 during a switch of theAT 20 from the source AN 21 to the target AN 22; the target AN 22 isadapted to perform a reset process for the AT 20 according to the Resetmessage sequence number sent by the source AN 21.

As shown in FIG. 2B, in this embodiment, the source AN 21 includes acommunication unit 210 and a processing unit 211. The communication unit210 is adapted to send the Reset message sequence number of the AT 20 tothe target AN 22 during the connected state handoff of the AT 20. Theprocessing unit 211 is adapted to confirm the connected state handoff ofthe AT 20 to the target AN 22, and add the Reset message sequence numberinto the message sent to the target AN 22.

In this embodiment, each message sent during information interactionbetween the AN1 and the AN2 is composed of a plurality of differentInformation Elements, and each Information Element contains acorresponding SSI information or/and configuration negotiationparameter. Therefore, the AN1 may add the Reset message sequence numberof the AT into the message sent to the AN2 by two methods.

In the first method, a new SSI information, i.e., a Reset Parameter SSI,is added into a SSI record Information Element of the A16-sessionTransfer Request Message and the A16-session Transfer Complete Message,and the Reset Parameter SSI contains the Reset message sequence numberof the AT.

As shown in Table 1, the Reset Parameter SSI information includes fieldsand lengths. The fields include Parameter Type, Length, and ResetSequence number of the source AN 21. The Reset Parameter SSI informationis filled in the SSI record Information Element in the manner given inTable 2.

TABLE 1 Field Length (bits) Parameter Type 8 Length 8 Reset Sequencenumber 8

TABLE 2 Length Reset Field (bits) Parameter Format ID 8 0 Reserved ID 10 Protocol Type 7 0x14 Protocol Subtype 16 0 Parameter Type 8 1 Length 81 Reset Sequence number 8 8

During a connected state handoff of the AT between the AN1 and the AN2,the AN1 and the AN2 perform a session information transfer through anA16 interface, and the Reset Parameter SSI information is transferredfrom the AN1 to the AN2 through the A16 interface.

As shown in FIG. 3, the detailed flow of the connected state handoff ofthe AT 20 between the source AN 21 and the target AN 22 is describedbelow. In Step 300, a connection is established between the AT and theAN1, so as to activate the AT.

In Step 301, the AN1 sends an A16-Session Transfer Request Message tothe AN2 for switching the AT to the AN2. The A16-Session TransferRequest Message contains a Reset Parameter SSI information.

In Step 302, the AN2 receives the A16-Session Transfer Request Messagesent by the AN1, and feeds back an A16-Session Transfer Response messageto the AN1.

In Step 303, the AN1 receives the A16-Session Transfer Response message,and then indicates the AT to switch from the AN1 to the AN2.

In Step 304, the AN1 sends an A16-Session Transfer Complete Message tothe AN2 to inform the AN2 that the switch is performed.

Since the parameters may be changed during the switch, the A16-SessionTransfer Complete Message also needs to carry the Reset Parameter SSIinformation.

In Step 305, the AT is switched from the AN1 to the AN2.

In the above first method, the Reset Parameter SSI information is addedin the existing Information Element of the A16 interface between the AN1and the AN2, thereby, the AN2 and the AT may maintain the new ResetParameter SSI information at the same time, so as to enhance thereliability of the Reset message sequence number carried by theinformation.

In the second method, an Information Element, i.e., a Reset ParametersInformation Element, is added into the A16-Session Transfer CompleteMessage sent from the AN1 to the AN2. The header information and fieldinformation contained in the Information Element are respectively shownin Table 3 and Table 4; and the way of filling the Information Elementin the A16-Session Transfer Complete Message is shown in Table 5.

TABLE 3 Information Element Name Identifier (Hex) Reset Parameters 17H

TABLE 4 Reset Parameters: A16 Information Element Identifier = [17H] 1Length = [01H] 2 Last Reset Message Sequence number 3 ‘1’ illustratesthe first byte, ‘2’ illustrates the second byte, and ‘3’ illustrates thethird byte.

TABLE 5 Information Element Information Element Direction Type A16Message Type Source → Target M AT-ID Source → Target Oa R Session StateInformation Record Source → Target Ob C Confirmed Unicast AccessTerminal Source → Target Oc C Identifier (UATI) Assigned UATI Source →Target Od C Long Code Mask UATI (LCM_UATI) Source → Target Oc CSignaling Link Protocol - D Parameters Source → Target Oe C (SLP-DParameters) Signaling Link Protocol - F Parameters Source → Target Oe C(SLP-F Parameters) Reset Parameters Source → Target O C ‘M’ illustratesthat the corresponding Information Element is must; ‘O’ illustrates thatthe corresponding Information Element is optional; ‘a’, ‘b’ . . . aretabs for remarking, which are illustrated in detail in 3GPP.

After the Reset Parameters Information Element is added into theA16-Session Transfer Complete Message, during the connected statehandoff of the AT between the AN1 and the AN2, the AN merely adds theReset message sequence number into the A16-Session Transfer CompleteMessage, thereby improving the transmission efficiency of the A16interface. On the other hand, the Reset message sequence number istransmitted as an individual Information Element, so as to enhance theobservability of the parameter. By means of the above two methods, afterthe AT is accessed to the AN2, when a reset process needs to beperformed for the AT, the AN2 sends the Reset message to the AT, and themessage sequence number contained in the Reset message is the ResetSequence number carried in the Reset Parameter SSI sent by the AN1plus 1. After the AT receives the Reset message delivered by the AN2, avalidity check is performed on the Reset message firstly. When the ATdetermines the Reset message is a valid message, a ResetAck message issent to the AN2, and the local SLP data structure, the correspondingbuffer, and the sequence number of the SLP packet are initialized.

Obviously, persons skilled in the may make various alternations andmodifications on the present invention without departing from the scopeor spirit of the invention. Thereby, the present invention tends tocover the alternations and modifications which fall within the scope ofthe claims of the present invention and the equivalent techniques.

1. A method for sending a reset message sequence number, comprising:initiating a connected state handoff of an access terminal (AT) betweena source access network (AN) and a target AN; and sending a resetmessage sequence number of the AT from the source AN to the target AN.2. The method according to claim 1, wherein the source AN sends anA16-Session Transfer Request Message to the target AN, and theA16-Session Transfer Request Message comprises the reset messagesequence number of the AT.
 3. The method according to claim 2, whereinan Information Element of the A16-Session Transfer Request Messagecomprises a session state information (SSI), and the SSI carries thereset message sequence number of the AT.
 4. The method according toclaim 1, wherein the source AN sends an A16-Session Transfer CompleteMessage to the target AN, and the A16-Session Transfer Complete Messagecomprises the reset message sequence number of the AT.
 5. The methodaccording to claim 4, wherein an Information Element of the A16-SessionTransfer Complete Message comprises a session state information (SSI),and the SSI carries the reset message sequence number of the AT.
 6. Themethod according to claim 4, wherein the A16-Session Transfer CompleteMessage comprises a new Information Element, and the Information Elementcarries the reset message sequence number of the AT.
 7. The methodaccording to claim 1, wherein the target AN updates the reset messagesequence number by adding one (1) to the reset message sequence number,and performs a reset process on the AT according to the updated resetmessage sequence number.
 8. A communication device, comprising: aprocessing unit, adapted to confirm a connected state handoff of anaccess terminal (AT) to a target access network (AN), and add a resetmessage sequence number of the AT into a message sent to the target AN;and a communication unit, adapted to send the reset message sequencenumber of the AT to the target AN during the connected state handoff ofthe AT.
 9. The communication device according to claim 8, wherein theprocessing unit is further adapted to add the reset message sequencenumber of the AT into an A16-session Transfer Request Message.
 10. Acommunication system, comprising: a source access network (AN) adaptedto initiate a connected state handoff of an access terminal (AT) andtransmit a reset message sequence number of the access terminal (AT)during the connected state handoff of the AT; and a target AN adapted toreceive the message sequence number and perform a reset process on theAT according to the message sequence number.
 11. The communicationsystem according to claim 10, wherein the source AN is further adaptedto add the reset message sequence number of the AT into an A16-SessionTransfer Request Message sent to the target AN.
 12. The communicationsystem according to claim 10, wherein the target AN is further adaptedto update the reset message sequence number by adding one (1) to thereset message sequence number sent, and then perform a reset process onthe AT according to the updated reset message sequence number.
 13. Thecommunication device according to claim 9, wherein the processing unitis further adapted to add the reset message sequence number of the ATinto an A16-session Transfer Complete Message sent to the target AN. 14.The communication system according to claim 11, wherein the source AN isfurther adapted to add the reset message sequence number of the AT intoan A16-Session Transfer Complete Message sent to the target AN.